Answer:
Step-by-step explanation:
The tree diagram is constructed and attached as an image below.
80% of the participants received medication, this means 20% received placebo. Among those who received medication, 76% reported improvement, this means rest 24% reported no improvement. Among those who received Placebo, 62% reported no improvement, this means rest 38% reported improvement.
The probability of P(Placebo and Improvement) will be = 20% x 38%
P(Placebo and Improvement) = 0.20 x 0.38 = 0.076 = 7.6%
This means there is 7.6% probability that those who received Placebo reported Improvement.
Answer:

Step-by-step explanation:
Average life of electric bulbs = 300 hrs
standard deviation = 45
Total no of bulbs tested = 100
Probability that sample mean is less than 295 =?
Using Central Limit Theorem

From table of normal distribution:

First you would simplify what's in the square root, to get root 20. If you want the exact number, and not the approximation, you would take out whatever squares are in that number (20=2*2*5) so your answer is 2root5.
However, if you want the approximation, simply plug it into your calculator and get 4.18154055.